Prior to the present invention polymer-polyol compositions were prepared by polymerizing one or more olefinically unsaturated monomers dissolved or dispersed in a polyol using free radical azo or peroxide initiators. In order to produce low-viscosity polymer-polyols containing low residual monomer levels, a vacuum stripping step was necessary which was often the most time consuming part of the entire manufacturing polymer-polyol manufacturing process. Thus, the vacuum stripping operation increased the total production time, increased the risk of personnel health problems by having to vacuum strip toxic monomers, and decreased productivity. Representative prior art methods for preparing polymer-polyols are disclosed in U.S. Pat. Nos. 4,172,825, 4,242,249, and 4,431,754.
The process of the present invention eliminates the lengthy and expensive vacuum stripping step of the prior art.